EFFECT OF PARASITISM BY APHELINUS-SPIRAECOLAE (HYMENOPTERA, APHELINIDAE) ON DEVELOPMENT AND REPRODUCTION OF SPIREA APHID (HOMOPTERA, APHIDIDAE)

The effect of parasitism by Aphelinus spiraecolae Evans & Schauff on d evelopment, survival, reproduction, and population growth of different life stages of the spirea aphid, Aphis spiraecola Patch, was assessed in the laboratory. Differences in aphid population growth were relate d to the life stage attacked. Aphids parasitized as 1st and 2nd instar s and 40% of those parasitized as 3rd instars died as 4th instars. App roximately 60% of aphids parasitized as 3rd instars and all parasitize d as 4th instars and adults reached maturity and produced a variable n umber of offspring, with those stung as adults producing more. Parasit ized adult aphids stopped producing offspring approximate to 6 d after parasitoid attack. Parasitism by A. spiraecolae decreased life span, fecundity, and intrinsic rate of increase of the spirea aphid and incr eased aphid doubling time at rates dependent on the host stage parasit ized. These data indicate that this parasitoid has potential as as a n atural enemy of the aphid and should be further evaluated.